Manufacture of benzaldehyde-2.5-disulfonic acil



'Pstente'd Mar. 31, 1925.

UNITED STATES PATENT OFFICE.

BENJAMIN BOSENBAUM, OF BUFFALC NEW YORK, ASSIGNOR TO NATIONAL ANILINE & CHEMICAL COMPANY, INC., OF NEW YORK, Y., A COB-PQBA'IION 01 NEW YORK.

xsnurnc'rusfn or BENzALnEnYnE a.s-msunromc AGE.

Io Drawing.

1 all whom it may concern:

Be it known that I, BENJAMIN ROSEN- BAUM, a citizen of the United States, resid- .ing at Buffalo, in the county of Erie, State of New York, have invented certain new and useful Improvements in the Manufacture of Benzaldehyde-2.5-Disulfonic Acid; and I do hereby declare the following to be a full, clear, and exact description of 10 the invention, such as will enable others skilled in the art to which it appertains to make and use" the same. This invention relates to im rovements in the manufacture of benzal ehyde-2.5- disulfonic acid-from 2-chlorbenzaldehyde- 5-sulfonic acid A Benzaldehyde 2.5-disulfonic acid or its salts has been heretofore obtained by heating 2-chlorbenzaldehyde-5-sulfonic acid in o a closed vessel or autoclave at an elevated temperature (around "BO -200 C.) with aqueous solutions of either sodium bisulfite or normal sodium 'sulfite. i The present invention is based upon the 25 discovery that benzaldehyde-2.fi-disulfonic acid can be easily obtained, in excellent yields and of good quality, by heating an aqueous solution of the sodium salt of 2-chlorbenzaldeh de-5-sulfonic acid with normal so sodium su fite at the boiling temperature at ordinary atmospheric pressure. The invention includes the further discovery that the yield can be somewhat increased if a. relatively small amount of sodium bisulfite is used in addition to the neutral sodium sulfite. The conversion of the 2-chlorbenzald'ehyde-5-sulfonic acid into benzaldeliyde- 2.5-disulfonic acid "can advantageously becarried out under re-fiuxing conditions, with 40 condensa ion and return of the water vaporized. a

The amount 1 sodium suiute used .is

4 capable of some variat on, but the maximum COIWBISIML appears to be obtained by the 5 use of aboutthree'mols of the normal sodium sulfite with one mol of2-chlorbenzaldehgffssulfonic acid and 1 0' mol of so dium ii'fta'the amount of sodium bisulfite being bout b a weight of the normsl sodium sulfite emp eyed "ihe Z-chiOrbenzaldehyds i ultonic acid used in the manufacture eenzaldehydeof free sulfuric anhydride, the temperature Applicant!!! filed July 24, 1922. Serial No. 677,185.

2.5-disunomc acid, according to the present invention, can be advantageously prepared according to the followin specific 56 example, but it will be understoo that the 2=chlorbenzaldehyde-fi-sulfonic acid can be produced by other suitable methods. The parts are byweight.

To 292 parts of fumin containing 26 per cent of ee sulfuric ans-,7, hydride, cooled to a temperature of there are introduced 150 parts orthochlor} v benzaldehyde, the mixture being well agi' tated and care being taken, by cooling, that the temperature does not rise above C. After all of the orthochlorbenzaldehyde has been added, there are slowly added 200 parts fuming sulfuric acid, containing per cent of the mixture being still maintained at or below 25 C. The mixture, under a itation, is thenheated to 85 C. .an main} tained at this tem rature until the sulfonation-is substantia ly complete as shown by a test sample giving a clear solution when added to dilutea ueous ammonia. -The reaction mixture is t en ured, withstirring,

onto 750-800 parts of ice and then sub ected to steam distillationin an atmosp ere containing carbon dioxide, obtained by slowly adding during the distillation a solution' of sodium carbonate, 'in order to recover a small amount" (around 2 to 5 per cent) of orthochlorbenzaldehyde which is usually present, and which has escaped sul- 'fonation. The hot, residual olution is then diluted with hot water to a. tit 2000 parts and neutralized by the addition of sodium carbonate, litmus being used as the indicator. During the neutralization, the temperatue of the solution is. ke at about -65-70 C.- in order to prevent either sodium sulfate or 2-chlorbenzaldehyde-5-sulfonic acid (either as free acid or sodium salt) from crystallizing out of solution. About 465470 parts of dry sodium carbonate are usually required to efl'ect neutralization.

The solution of the sodium-salt of 2-chlor-' benzaldehyde-fi-sulfonic acid thus obtained can be used dir tly for subsequenttreatment in the 'nfihfactrire of, benzaldehyde- 2.5-disulfo1iic acid. 'Themethod of treatment is illustrated by the followingspecific sulfuric acid, 60

1 thereto.

To the neutral and well stirred solution, prepared as above described, there are added 1170 parts of a 20% neutral solution of sodium sulfite (neutral to pheuolphthalein) and then 35.5 parts of dry powdered sodium bisulfite, and the mixture is heated to boiling under a. reflux condenser at atmospheric pressure until the reaction is 001m plete as indicated by no further increase in the amount of sodium chloride formed. When the reaction is complete, the solution is acidified by the addition of concentrated sulfuric acid and then boiled until the excess of sulfurous acid is expelled. The solution thus obtained, and which contains chiefly benzaldehyde-2.5-disulfonic acid and sodium sulfate, may be treated in any suitable and Well known mariner for the isola tion of the benzaldehyde-2.5-disulfonic acid, or the solution may be employed directly in the production of triphen lmethane coloring matters of the malac ite reen series by "condensing the benzaldehy e-2.5-disulfonic acid with alkylated aromatic amines or their derivatives and subsequently oxidi ing the leuco dyes thus obtained to the corresponding coloring matters.

In the process of the present lllvkzuuull it will be seen that neither high temperatures nor high pressures are used to bring about the reaction and that closed vessels or autoclaves are unnecessary, and that the conversion" of 2-chlorbenzaldehyde-5-sulfonic acid into benzaldehyde-2.5-disulf0nic acid is carried out in aqueous media at the boiling temperature and under refluxing conditions at ordinary atmospheric pressure. Excellent yields are nevertheless obtained and the benzaldehyde-2.5-disulfonic acid is of sufficient purity to permit its direct use, without isolation, in the manufacture of triplicnylmethane dyestufis.

The reaction can be oroughtaoout using normal sodium sulfite alone, but somewhat more by-products appear'to be formed than when a little sodium bisulfite is also used. It is accordingly advantageous to make use of a small amount of sodium bisulfite in addition to the normal sodium sulfite, and somewhat larger yields of the benzaldehyde- 2.5-disulfonic acid can, be thus obtained. The amount of sodium bisulfite used, however, is not sufiicient to give to the charge an acid reaction (i. e. acid to litmus).

I claim:

1. The process of making a salt of benzaldehyde-2.5-disulfonic acid, which comprises heating a salt of 2-chlorbenzaldehyde- 5-sulfonic acid with alkali sulfite in the resence of water under ordinary ,atmosp eric pressure.

2. The process of making a sodium salt of benzaldehyde2.5-sulfonic acid, which comprises heating the sodium salt of. 2- chlorbenzaldehyde-ii-sulfonic acid with normal sodium sulfite in the presence of water at the boiling temperature of the mixture under atmospheric ressure.

3. The process 0 making a sodium salt of benzaldehyde-2.5-disulfonic acid, which comprises heating the sodium salt of 2-chlorbenzaldehyde-o-sulfonic acid with normal sodium sulfite in the resence of water and sodium sulfate at boi 'ng temperatures under a reflux condenser and at ordinary atmospheric pressures 4. The. process of making EISOQIUIH Salli of benzaldehyde-2.5-disulfonic acid, which comprises heating to the boil' temperature the neutral sodium salt of fiil'orbenzaldehyde-5-sulfonic acid with sodium sulfite containing sodium bisulfite in the presence of water under atmos heric pressure.

- 5. The process 0 makin the sodium salt of be nzaldehyde-2.5-disul onic acid which comprises heating the sodium salt of 2-chlorbenzaldehyde-fi-sulfonic acid with normal sodium sulfite and sodium bisulfite in the presence of water, the heating being carried out at the boilin ture at atmosp eric ressure, and the V amounts of sodium so be and sodium bisulfite bein approximately three mole of sodium sul to and three-tenths of a mol of sodium bisulfite to one mol of the sodium salt of 2-chlorbenzaldehyde-5-sulfonic acid. 6.'In a process of reducing a salt of benzaldchyde-2.5-disul onic acid by sub'ecting a'saltfof 2-chlorbenzaldehyde-5sul onic acid to the action of normal sodium :sulfite.

temperature of the mixin the presence of water, the improt pment zaldehyde-2,5-disulfonic acid, wherein a salt of 2-ch10rbenzaldehyde-fi-sulfonic acid 'is heated with normal sodium sulfibe'in the presence of water, the im rovement which comprises adding, before the heating operation, sodium bisulfite.

8. In a process of producin a salt of benzaldehyde2.5-disulfonic aci wherein a salt of 2-chlorbenzaldehyde-5-sulfonic acid is heated with normal sodium sulfite in the presence of water at about the boiling tern= perature under atmospheric pressure, the improvement which comprises adding, before the heating operation, an amount of sodium bisulfite equal to about ten rcent by weight of the normal sodium sulfide employed.

9. In a process of roducing a salt of benzaldehyde-2.5-disulf dnic acid by subjectmg a salt of 2-chlorbenzaldehyde-5-sulfonic acid to the action of an alkali metal sulfite 1n the presence of water, the improvement a process of producing asalt of be-n-.

charactexfiznd by causing the reaction to occur 2:: approximately atmobpneric pressures.

10. The ywucuss of making a salt (If bun zz-ddeuyk-Qi; disulfoni acid, which comprf'zsrm heating]; under nmje'uxilnalvly ordinary uhnuhpheric prvsmre a salt of z-dllww bcnzuldehydP .lsulikmlc acid wiLh a mmm of aikuli Mn bllliiflq alkali blsulfiw and a W k511i v1.1a buli'zme m the presence of nut-0r,

11. In a process of producing asalt of hen zaldollydo2.5-disu1fonic acid, wherein a salt of 2-chlurhcnznldehydwS-sulfonic acid is heated under approxinmtely atmospheric pressure with sodium sulfite in the presence of water and podium sulfate, the impr0vement whivh uomprises adding, before the matin operation, sodium bisulfite.

In bcstimon whereof I affix m. 7 si mature.

BIENJAMIN ROSE B UM. 

